The publication of the Chinese patent application CN1252353A discloses an invention named by “Ink tank, assembly and printing device using the assembly”, the structure of the ink cartridge thereof has been described by an embodiment shown in FIG. 5 of CN1252353A. This ink cartridge is a type of the one having two chambers, an ink absorbent material, an ink supply port, and an air hole communicated with the atmosphere are provided in one chamber. The other chamber is a liquid storing chamber that is substantially closed. These two chambers are communicated with each other through a channel formed near the bottom portion of a partition wall. As the print head consumes the ink absorbed by the ink absorbent material, ink in the liquid storing chamber will be supplied to the ink absorbent material through the communicating channel between these two chambers. When the negative pressure in the liquid storing chamber has increased gradually during the ink supply, air then comes from the air hole and through the ink absorbent material will be supplied into the liquid storing chamber via the communicating channel, as a result of which the negative pressure in the liquid storing chamber will decrease, forming a substantially constant negative pressure applied to the print head. Therefore, ink supplied to the print head is kept stable. Furthermore, at the bottom of the liquid storing chamber, there is a triangular prism having a shape of an isosceles triangle whose apical angle is 90°. This prism together with a photoelectric device in the printer constitute an ink-out detection mechanism, the detecting principle of which is as follows: when the ink cartridge is sufficiently filled with ink, once the incident light comes to a plane that contains one oblique portion of the triangle, it will refract into the ink and be absorbed by the ink, so there may not any light signal received by a photoreceptor; when ink is consumed to be below the refracting point of the prism, the incident light will be reflected twice respectively by two planes that contain two oblique portions of the triangle respectively, and then comes to the photoreceptor parallelly, after the photoreceptor has received the light signal, the printer will send an ink-out indicative signal.
It should be pointed out that, sending the ink-out indicative signal by the printer only means that there is not any ink in the liquid storing chamber, while the other chamber still has a certain amount of ink because of the capillary action of the ink absorbent material therein. Therefore, even having received the ink-out indicative signal, a user still may continue to print for a certain amount. This offers an advantage to the printer user that he may deal with the subsequent printing operation. For example, after having received the ink-out signal, the user may continue to print numbers of the standard sheets in general. If the page numbers to be printed are beyond this number, it will be preferable to replace the ink cartridge, so as to avoid doing it at the midcourse of printing on several pages.
Furthermore, the present applicant once developed an ink cartridge, which mainly consists of: a gasbag assembly, which is made up of a cartridge body, a cap, a gasbag seating, a gasbag and an elastic retainer ring; a check valve assembly, which is made up of a valve cap, a valve body and a filter; and a sealing ring disposed in the ink supply port, the moving direction or the center line of the valve body is parallel with the center line of the ink supply port.
The most serious problem about the ink cartridge that takes the first structure described above is that the ink amount contained in each ink cartridge is relatively low. The ink absorbent material generally makes use of a sponge, which will occupy most volume of the chamber, so the volume used for storing ink becomes small relatively.
The cartridge taking the second structure described above has been used in some types of the printers and has achieved a good effect for ink supply. But with regard to some high-speed inkjet printers, in which the ink cartridge and the print head move back and forth simultaneously with a high speed, the acceleration at the turn-back point may be extremely high. In this case, the periphery of the valve body whose centerline is perpendicular to its moving direction will be subject to the inertia effect. The valve body made of rubber has a certain length in the axial direction, so a hole on the valve body will lose its stability and deform under the inertia effect applied to its periphery. Although this deformation can recover immediately after the inertia force has disappeared, there is still a certain amount of ink passing through the check valve, which ought to be in close state, during the deformation and the recovery. This will result in the ink to be excessively supplied, decreasing the printing quality.
Furthermore, with respect to some types of the printers, such as a color inkjet printer using five color cartridges, the chamber of the cartridge is so narrow that the dimension needed to dispose the check valve in a certain direction is smaller or slightly larger than the minimum dimension required for mounting the valve assembly, thus causing this ink cartridge not able to be assembled or causing the assembling to become difficult. Accordingly, assembling the ink cartridge equipped with the check valve in a narrow ink chamber will decrease the pass rate of products.
In addition, the ink cartridge using a check valve to control the ink supply has a certain space between an outlet of the check valve and the ink supply port. Generally, in order to prevent the ink from volatilizing, the ink supply port of an unused ink cartridge is always sealed with a sealing membrane or a sealing cap. However, with respect to some types of the printers that employ an ink supply needle to pierce the sealing membrane and to come into the ink supply port, when the ink supply needle is coming into the space described above, the ink in this space will be probably subject to an instant extrusion because of the reverse cut-off provided by the check valve. As a result of this, the ink will drop out along with the ink supply needle, contaminating the printer or the printing medium. Furthermore, when the ink cartridges are produced by a negative pressure ink-filling method, this space can not draw the negative pressure from the ink supply port located in the cartridge cap, causing the ink not to be filled or to be insufficiently filled into this space. Some printers with print heads having small self-sucking force will occur such a phenomenon during use that the ink is discontinuously supplied.